This study tests a drug called NMRA-335140 in adults with Bipolar II Disorder, a condition causing mood swings between depression and hypomania. The study is randomized (participants are randomly chosen to get the drug), double-blind (neither participants nor researchers know who gets the drug), and placebo-controlled (some people get a fake treatment). It lasts about 14 weeks total, including a 6-week treatment period.

Eligibility: You must have a current major depressive episode lasting 4-12 weeks and score 25 or higher on a depression questionnaire called MADRS. Certain mental health conditions and substance use disorders mean you can't join.

• Study Length: Up to 14 weeks including screening, treatment, and follow-up.
• Visits: Regular visits are required during the study period.
• Risks: Possible side effects or no improvement in depression symptoms.

In this study, you will either receive NMRA-335140 or a placebo pill. This is to find out if NMRA-335140 can help reduce depression symptoms in people with Bipolar II Disorder. Always discuss with your doctor before joining a study.